Typically, a conventional ratchet wrench has an elongate handle attached to a head portion. The head portion contains a ratchet mechanism that causes the drive lug to rotate in a selected clockwise or counterclockwise direction when the handle is repeatedly swung back and forth through an arcuate path. In particular, when a fastener such as a bolt or screw is tightened or loosened, rotational force is applied to the fastener when the handle is swung arcuately in one direction, but the ratchet mechanism allows the wrench handle to be swung in the reverse direction without rotating the drive lug in the opposite direction and, hence, without applying force to the fastener.
Conventional ratchet wrenches perform adequately in many situations. However, when the space available around the fastener head restricts arcuate movement of the handle to a relatively small angle, a conventional ratchet wrench may be unusable or, at best, cumbersome and inconvenient to use. One proposed solution to this problem is a dual-mode ratchet wrench in which the drive lug can also be made to rotate when a sleeve-like section or portion of the handle is rotated about the longitudinal axis of the handle. In such arrangements, the sleeve-like section of the handle is coupled to the drive lug by means of a shaft and double gear system so that rotating or twisting the handle sleeve in one direction will cause the drive lug to rotate in the clockwise direction, while rotating the handle in the opposite direction will cause the drive lug to rotate counterclockwise.
One drawback of the prior art dual-mode ratchet wrenches results from the use of a locking mechanism for engaging and disengaging the sleeve-like handle region with the bevel gear and other elements of the associated drive system. Such a mechanism requires the person using the wrench to use both hands to perform a change in the mode of wrench operation and may require that the wrench be removed form the workpiece in order to accomplish the change. Removal and replacement of the ratchet wrench in a limited space situation is inconvenient and results in wasted time. Attempts have been made to provide a dual-mode wrench in which the mode of wrench operation can be selected with one hand. Such prior art arrangements of this type utilize a handle knob or sleeve that is permanently attached to a shaft that in turn is permanently coupled to the drive lug. The drawback to this arrangement is that as the wrench is used in its reciprocating mode, the handle will rotate in the operator's hand. Other prior art devices overcome this by incorporating a ratcheting mechanism in the sleeve to connect the sleeve to the drive shaft, thus preventing rotation of the sleeve in the operator's hand. This arrangement requires two ratcheting assemblies, one in the drive unit and one in the handle. This has the disadvantage of making the tool heavier and more difficult to operate. In addition, this configuration is complex and costly to manufacture.